Method for improving the odor of hydrocarbon distillates with lead dioxide



nited States Patent METHOD FOR IIVIPROVING THE ODOR OF HY- lgylggfiiARBoN DISTILLATES WITH LEAD DI- Robert W. Snyder, Sheflield Lake, and Richard J.

De Gray, Shaker Heights, Ohio, assignors to The Stand- Oil Company, Cleveland, Ohio, a corporation of No Drawing. Filed June 25, 1957, Ser. No. 667,992

1 Claim. (Cl. 208-295) The present invention relates to a method of improving the odor of hydrocarbon distillates. More particularly, the invention relates to a method wherein the odor of certain petroleum fractions is ameliorated by contacting such fractions with lead dioxide.

Certain hydrocarbon distillates derived from crude petroleum oil are widely employed as solvents in a variety of industries. That fraction of crude petroleum oil boiling in the range of 100 F. to 400 F. which is known to the art as naphtha has been used extensively as a solvent in the dry cleaning of clothing and other textiles. Another important use of this naphtha fraction is as a solvent in the manufacture of paint and related products. In these applications it is obviously important that the naphtha be free of any obnoxious odor, and where possible it is desirable that the odor of the naphtha not have an unpleasant reaction upon the human olfactory nerve.

Most naphthas do not possess a pleasant odor as produced since they contain mercaptans and other odoriferous organic compounds. Consequently, some method of treating naphthas is generally resorted to in the solvent manufacturing industry to improve their odors. Various methods are known to the art for accomplishing this purpose.

We have now discovered that the odor of a petroleum naphtha may be appreciably improved by contacting the naphtha with lead dioxide (PbO This discovery is quite surprising since other lead compounds have no elfect whatever on the odor of naphtha under similar treating conditions. For example, litharge (PbO) has been found to have no appreciable effect on the odor of a petroleum naphtha.

In carrying out the process of this invention, we prefer to conduct the process in a vessel packed with solid lead dioxide by percolating the stock to be treated therethrough. Alternately lead dioxide may be mixed with the stock to be treated and the mixture is then passed to a settling zone. In the latter embodiment of the invention, a portion of the lead dioxide may be continuously withdrawn from the settling zone and admixed with fresh feed.

In general, the operation is carried out at ambient temperatures but temperature is not critical and other temperatures have been found to be operable. Temperatures above the boiling point of the stock are preferably avoided in order that the process can be carried out without pressure apparatus. The method of the invention may be conducted under super-atmospheric pressure, but pressure is in no way critical and the process is usually conducted at atmospheric pressure. There appears to be 2,970,104 Patented Jan. 31, 1961 very little deterioration in the effectiveness of the lead dioxide upon continued use. However, periodic replacement of the lead dioxide is contemplated within the scope of this invention.

The lead dioxide which is employed in the process of this invention should be in a solid particle form. Particle size is not critical and any convenient size may be employed in this process.

It has been found that contact times of about 60 to about 120 minutes are effective to improve the odor of most stocks. The contact time is defined herein as the total free volume of lead dioxide divided by the volume of hydrocarbon passing thereover per minute. Longer contact times may be employed but there is generally no advantage to this since the odor will be improved to only a small extent upon such continued treatment. 7

The following example is illustrative of the preferred embodiment of our invention:

A virgin naphtha solvent boiling from 300 F. to 400 F. obtained by distillation from crude Mid-Continent petroleum Was percolated through a bed of lead dioxide at the rate of 0.011 gaL/min. at a temperature of F. and atmospheric pressure. The lead dioxide bed was contained in a conventional steel treating vessel having inlets and outlets as is well known to the art and it was composed of 1 lb. of lead dioxide having a bulk density of 92.4 lbs./cu. ft. The naphtha fed to the process had a distinct unpleasant odor, but after treatment no unpleasant odor was detected. A total of 17.5 gal. of the naphtha were treated with no apparent decrease in the efiectiveness of the lead dioxide.

While this invention has been described particularly with reference to petroleum naphthas, this was done merely for the purposes of illustration and the invention is not intended to be limited thereto. Other petroleum fractions such as coker overhead gas oil, catalytic cycle stocks and kerosene may be treated by the method of our invention with efficacy. Accordingly, we desire this application for Letters Patent to cover all such embodirnents of the invention as will reasonably fall within the scope of the appended claim.

We claim:

A process for improving the odor of a petroleum naphtha, boiling in the range between about to about 400 F. and having a normally unpleasant odor, consisting of the step of contacting said naphtha in the liquid phase at a temperature of about 70 F. with a bed of lead dioxide in solid particle form so that the contact time is about 60 to about minutes, whereby the odor of said naphtha is ameliorated.

References Cited in the file of this patent UNITED STATES PATENTS 564,341 Salathe July 21, 1896 607,017 Colin July 12, 1898 1,767,356 Fischer June 24, 1930 2,338,941 Howard Jan. 11, 1944 2,369,558 Gilbert Feb. 13, 1945 FOREIGN PATENTS 48 Great Britain Ian. 6, 1863 748.267 France July 1, 1933 

